I'm certain I have lots of bacteria in my stomach; I probably have a significant number of viruses there as well. The term "stomach whatever" is sometimes colloquially used to mean "an illness that...
Depends how serious it is. The best thing to do is just to sit down and drink water. If it is very troubling, go to the doctor. Sometimes it is just a cramp.
You can get a stomach virus by hanging a round a person who already has one well not if you touch him or her but if you drink after them or they sneeze or cough in your face if you kiss them then...